Inflorescence and Flower Development in Orchidantha chinensis T. L. Wu (Lowiaceae; Zingiberales): Similarities to Inflorescence Structure in the Strelitziaceae

Premise of research. The monotypic Lowiaceae remains the least-known family in the plant order Zingiberales, yet it may hold an important key to unraveling the phylogenetic placement of the families Musaceae, Heliconiaceae, Strelitziaceae, and Lowiaceae. After nine phylogenetic studies, the (Lowiaceae, Strelitziaceae) clade is the only stable clade that has emerged in this half of the order. This study was undertaken to verify the unusual inflorescence and flower structure in Orchidantha and to search for new characters that might be used in future phylogenetic analyses. We describe both inflorescence and flower development in a previously unstudied species; confirm inflorescence morphology in the genus; and compare the structure of the inflorescence in the Lowiaceae with that of the Strelitziaceae, its potential sister group. Methodology. Standard collection and SEM procedures were used to collect and prepare the material for study. Pivotal results. The inflorescence of Orchidantha is borne at the end of a vegetative shoot and is composed of two lateral branches that each bear four bracts and a single flower before aborting. The fourth bract and its associated flower form the highly reduced flower cluster (florescence) that characterizes this genus. In technical terms, Orchidantha has a polytelic synflorescence that lacks a main florescence (it has a truncated polytelic synflorescence) and bears solitary flowers in coflorescences on determinate enriching branches. The enriching branches produce a fixed number of bracts before aborting (i.e., they are special paracladia). Many of these features are shared with the Strelitziaceae. Conclusions. Similarities between the Lowiaceae and Strelitziaceae include inflorescence structure; the presence of a long prolongation of the ovary; and a delay in the formation of the third sepal during flower development, a character that is also shared with the Musaceae. Inflorescence and flower structure is now well established in this small but important family